Novel wet cleaning solutions for EUV masks

Removal of metallic contaminants on EUV masks has become increasingly critical for achieving smaller feature sizes in both advanced logic and DRAM semiconductor manufacturing processes. One major issue with EUV scanners is that they may carry Sn containing defect sources toward the EUV mask, causing serious yield and throughput problems. Once exposed to EUV radiation, contaminated Sn particles on the EUV mask are difficult to remove from the surface due to thermal aging and subsequent deformation. Conventional wet cleaning processes using sulfuric acid and hydrogen peroxide mixture (SPM) not only exhibit limited removal efficiency for metal particles but also reduce the EUV mask's lifetime due to undesired damage on exposed surfaces. Herein, we report the development of an alternative wet solution, EtchSolv™ HSE6000, which selectively facilitates the dissolution of Sn and other metallic particles while exhibiting excellent compatibility with the Ta-based absorber layer and Ru capping layer. This investigation includes a quantitative comparison of the dissolution rates of metal contaminant sources following wet chemical treatment, analyzed using ICP-MS. Notably, the efficiency of Sn particle removal depends on the type of contaminated surface and the effects of thermal aging.